When Shimano went to 10-speed with 2004 Dura-Ace, they did a major re-design of the ergonomics of their brifters. The thing they most tout is that the shift levers move at a slight rearward angle as you push them sideways, conforming better to the sweep of the rider's fingers. This is a nice enough feature, but to me the greater improvement is the complete re-shaping of the brifter body. I was never a big fan of the 9-speed model. I ran an Ultegra set on my Hetchins for a while, but wound up removing it and installing Campagnolo Ergo instead.

The re-shaped 10 speed brifters work much better for me. In addition to a more comfortable normal hood position, they have added an extra riding position! The body sticks up a bit higher in front and provides a very nice place for the rider to grip so the side of the hand rests on top of the hood, and the lower fingers wrap nicely around the projecting top. This gives a position somewhat reminiscent of an aero bar, and I like it a lot as an alternate cruising position.

This design, introduced in 2004 Dura-Ace, "trickled down" to Ultegra when that group went 10-speed in 2005, and to 10-speed 105 in the 2006 modlel year.

Frankly the extra sprocket isn't that big a deal to me, but I like the 10-speed brifters' ergonomics very much.